Studies On Synthesis,Characterization And Catalyic Properties Of Transition Metal Complexs Based On Pyridyl-1,2,4-triazole And Polycarboxylic Acid

In the field of coordination chemistry, it is a great challenge to synthesize coordination polymers with intriguing structures and properties due to the diversified conformations and coordination modes of ligands.In this contribution, twelve types of conformations of pyridyl-1H-1,2,4-triazole(Hbpt) have been optimized by density functional theory (DFT) at the basis of 6-31G**.Based on the guidance of the calculated results, we probed into the directional construction and ordered assembly for functional complexes with carboxylic acids as coligands, six novel compounds, 3,3’-Hbpt·2H2O (1), [Co2(2,3’-bpt)4](2), [Zn(2,3’-bpt)(pta)0.5(H2O)](3), [Co(2,4’-bpt)3]·H3btc(4), [Co(3,3’Hbpt)2(H2O)4]·(C6H8O4)·6H2O(5) and. [Cd2(oba)3(3,4’-Hbpt)2](6) have been successfully synthesized and characterized by single-crystal X-ray diffraction, elemental analysis, infrared spectra analysis and thermogravimetric analysis. For the six compounds, the catalytic properties on the Ihermal decomposition of ammonium perchlorate (AP) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) have been discussed. The concrete research contents and conclusions are as follows.1. We have prepared five isomeric ligands of pyridyl-1H-1,2,4-triazole. Twelve types of conformations of the Hbpt ligands have been optimized by density functional theory. Moreover, the preferred conformations and coordination models are predicted, providing the theoretical foundation for the design of complexes.2. According to the results of theoretical calculation,2,4’-Hbpt inclines to cis-Ⅰ configuration and 2,3’-Hbpt prefers cis-Ⅰ and trans-Ⅰ configurations to chelate metal nodes, whereas 3,3’-Hbpt likes cis-Ⅰ and cis-Ⅱ configurations to bridge metal nodes, and 3,4’-Hbpt inclines to trans-Ⅰ configuration to promote the size and flexibility of the structural framework, which is advantageous to synthesize the polymers with larger size.3. Obviously, introducing carboxylic acids into the reaction systems influences effectively on the structures of Hbpt-based complexes. Carboxylic acid was considered as counter ion in the construction of the supramolecular compounds with 3,3’-Hbpt ligand, while as template in the case of 2,3’-Hbpt. For the systems of other ligands, carboxylic acids coordinate with the metal ions to tune the targeted frame structures.4. The effects of complexes 2-6 on the thermal decomposition of AP and RDX are investigated as well. The results demonstrate that complexes 2-6 and exhibits favorable catalytic capability in the decomposition processes of AP or RDX.